The present invention relates to an illuminating apparatus using light emitting diode chips, a method for fabricating the illuminating apparatus, and a display apparatus which uses the illuminating apparatus as a back light for a non-light emitting display panel.
An improved light emitting efficiency of recent light emitting diodes (LED) drives an ever replacement of light sources for a variety of illuminating apparatuses from fluorescent lamps to light emitting diodes. This is because the light emitting diodes have many features such as smaller size, ability to generate multiple colors, ease of control, low power consumption and the like. However, since light output of a single light emitting diode is still insufficient in applications which require high light outputs, a plurality of light emitting diodes are arrayed to make up an illuminating apparatus.
For example, in a liquid crystal display, an illuminating apparatus is made up of an array of plural light emitting diode packages, which emit light red, green, and blue light, respectively, for use as a back light, as described in SID03 Digest, pp. 1262-1265 (2003). Also, as described in SID04 Digest, pp. 1222-1225 (2004), a red, a green, and a blue light emitting diode are disposed in the same package, a plurality of which are arranged in combination with light guiding plates to build an illuminating apparatus which is used as a back light. Further, a signal light for automobile, for example, employs an illuminating apparatus which has light emitting diodes mounted on a series of lead frames, as described in JP-A-8-339707.
However, when light emitting diodes are packaged and a plurality of the resulting packages are arrayed as described in SID03 Digest, pp. 1262-1265 (2003) and SID04 Digest, pp. 1222-1225 (2004), each package must be again mounted on a printed circuit board by soldering or the like, thus causing an increased cost for the mounting.
On the other hand, when a plurality of light emitting diodes are arrayed on a series of lead frames as described in JP-A-8-339707, the mounting cost can be reduced because the light emitting diodes are connected to the lead frames at a smaller number of spots. However, since a plurality of light emitting diodes are mounted on a series of lead frames such that they are electrically connected in series, all of the plurality of light emitting diodes are regarded as defective and discarded if even one light emitting diode is involved in defective mounting or is defective per se. Therefore, the yield rate is lower when light emitting diodes are mounted on a series of lead frames, as compared with package-by-package mounting on a printed circuit board.